Toroidal droplets: instabilities, stabilizing and nematic order

View/Open

Date

Author

Metadata

Abstract

The goal of this thesis is to study the ground or metastable state structure of nematic liquid
crystal systems confined inside handled shapes such as a torus or double torus. We begin our work
by introducing a new method to generate a toroidal droplet from a Newtonian liquid inside another,
immiscible, Newtonian liquid. In this situation, a toroidal droplet is unstable and follows one of two
routes in transforming into a spherical droplet: (i) its tube breaks in a way reminiscent to the breakup
of a cylindrical jet, or (ii) its tube grows until it finally coalesces onto itself. However, to be able to
probe the nematic structure, we need to address the issue of instabilities. This is done by replacing
the outer liquid with a yield stress material, which ultimately leads to the stabilization of the toroidal
droplet. Through the experimental investigation, we are able to establish the stabilization conditions.
Finally, we generate and stabilize toroidal droplets with a nematic liquid crystal as the inner liquid
and a yield stress material as the outer medium. Here we observe that in the ground state, the
nematic liquid crystal exhibits an intriguing twisted structure irrespective of the aspect ratio of the
torus. While there are no defects observed in a toroidal droplet case, two defects with -1 topological
charge each emerge each time we increase the number of handles.